#include <stdio.h>
double countx(int n)
{
	int i;
	double x=2.00;
	for(i=1; i<=n-1; i++)
	{
		x = x*0.98;
	}
	return x;
}
int main(int argc,char *argv[])
{
	int step;
	double sum=0;
	double x;
	scanf("%lf",&x);
	int n=1;
	while(1)
	{
		sum = sum+countx(n);
		if(sum>x)
		{
			break;
		}
		n++;
	}
	printf("%d\n",n);
	return 0;
}
